From 4e752f63b94b71d901a1933a1bb121332fffe96b Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Fri, 17 Feb 2017 10:09:49 -0800
Subject: [PATCH] [core] Redo approach to unsupported VAO extension

---
 src/mbgl/gl/context.cpp | 19 ++++++++++---------
 src/mbgl/gl/context.hpp |  2 ++
 src/mbgl/gl/segment.hpp | 17 +++++++++++------
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 5726eca5d..9c2031ccf 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -122,17 +122,17 @@ UniqueTexture Context::createTexture() {
     return UniqueTexture{ std::move(id), { this } };
 }
 
+bool Context::supportsVertexArrays() const {
+    return gl::GenVertexArrays &&
+           gl::BindVertexArray &&
+           gl::DeleteVertexArrays &&
+           !disableVAOExtension;
+}
+
 UniqueVertexArray Context::createVertexArray() {
+    assert(supportsVertexArrays());
     VertexArrayID id = 0;
-    if (gl::GenVertexArrays && !disableVAOExtension) {
-        MBGL_CHECK_ERROR(gl::GenVertexArrays(1, &id));
-    } else {
-        static bool reported = false;
-        if (!reported) {
-            Log::Warning(Event::OpenGL, "Not using Vertex Array Objects");
-            reported = true;
-        }
-    }
+    MBGL_CHECK_ERROR(gl::GenVertexArrays(1, &id));
     return UniqueVertexArray(std::move(id), { this });
 }
 
@@ -529,6 +529,7 @@ void Context::performCleanup() {
     }
 
     if (!abandonedVertexArrays.empty()) {
+        assert(supportsVertexArrays());
         for (const auto id : abandonedVertexArrays) {
             if (vertexArrayObject == id) {
                 vertexArrayObject.setDirty();
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index d1be79424..9d3ecec66 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -39,6 +39,8 @@ public:
     UniqueProgram createProgram(ShaderID vertexShader, ShaderID fragmentShader);
     void linkProgram(ProgramID);
     UniqueTexture createTexture();
+
+    bool supportsVertexArrays() const;
     UniqueVertexArray createVertexArray();
 
     template <class Vertex, class DrawMode>
diff --git a/src/mbgl/gl/segment.hpp b/src/mbgl/gl/segment.hpp
index 7ce90e53a..b2761a210 100644
--- a/src/mbgl/gl/segment.hpp
+++ b/src/mbgl/gl/segment.hpp
@@ -3,6 +3,7 @@
 #include <mbgl/gl/context.hpp>
 #include <mbgl/gl/vertex_buffer.hpp>
 #include <mbgl/util/optional.hpp>
+#include <mbgl/util/logging.hpp>
 
 #include <cstddef>
 #include <vector>
@@ -32,12 +33,11 @@ public:
               BufferID indexBuffer_,
               const typename Attributes::Locations& attributeLocations,
               const typename Attributes::Bindings& attributeBindings_) const {
-        if (!vao) {
-            vao = context.createVertexArray();
-            context.vertexBuffer.setDirty();
-        }
-
-        if (*vao) {
+        if (context.supportsVertexArrays()) {
+            if (!vao) {
+                vao = context.createVertexArray();
+                context.vertexBuffer.setDirty();
+            }
             context.vertexArrayObject = *vao;
             if (indexBuffer != indexBuffer_) {
                 indexBuffer = indexBuffer_;
@@ -46,6 +46,11 @@ public:
             }
         } else {
             // No VAO support. Force attributes to be rebound.
+            static bool reported = false;
+            if (!reported) {
+                Log::Warning(Event::OpenGL, "Not using Vertex Array Objects");
+                reported = true;
+            }
             context.elementBuffer = indexBuffer_;
             variableBindings = {};
         }